Explain how mutations change the DNA sequence and their possible effects, and describe how genetic technologies such as selective breeding and genetic engineering are used (NYSSLS LS3, cause and effect; structure and function).

What this topic is asking

NYSSLS LS3 wants you to explain how mutations change the genetic code and what effects they can have, and to describe how humans use genetic technology. On the Life Science: Biology Regents this often comes as a cluster about a changed gene and its consequences, or about the benefits and concerns of modifying organisms. The crosscutting concept is cause and effect.

What a mutation is

Because the base sequence codes for proteins (see protein synthesis and gene expression), a mutation can change a codon, which may change an amino acid, which may change the protein's shape and function.

The effects of mutations

This three-way classification is exactly what the exam expects. Whether a mutation matters depends on where it is and how it changes the protein.

Inherited versus non-inherited mutations

A crucial distinction: only mutations in gametes (sex cells) can be passed to offspring, because the gametes form the next generation. A mutation in a body cell (for example a skin cell) affects only that individual and is not inherited (though it can cause problems such as cancer in that person). The exam often tests this by asking why a particular mutation is or is not passed on.

Mutations as the source of variation

Mutations are the original source of new alleles. Meiosis and fertilization then shuffle existing alleles into new combinations (see meiosis and sexual reproduction), but the alleles themselves first arose by mutation. This genetic variation is what natural selection acts on, linking this topic to evolution (see natural selection and adaptation).

Genetic technologies

Humans deliberately change the genetics of other organisms:

• Selective breeding (artificial selection): choosing organisms with desired traits and breeding them over many generations, so the desired alleles become more common. It works with existing variation and is slow.
• Genetic engineering: directly inserting or altering specific genes, often moving a gene from one organism into another (for example inserting a human gene into bacteria so they make insulin). It is fast and precise but more technically demanding.

Both bring benefits (higher crop yields, disease or pest resistance, medicines, added nutrients) and concerns (effects on ecosystems and biodiversity, ethical questions, economic impacts). The exam may ask you to weigh one of each.

Try this

Q1. Define a mutation and state the three possible effects it can have on a protein. [2]

• Cue. A change in the DNA base sequence; effects can be harmful, beneficial or neutral (no effect).

Q2. Explain the difference between selective breeding and genetic engineering. [2]

• Cue. Selective breeding chooses organisms with desired traits to breed over generations (using existing variation); genetic engineering directly inserts or alters specific genes, often between organisms.